This study aims to: (1) Describe the type and extent of changes in nutritional status that develop across the spectrum of HIV infection during its treatment, including etiology of nutritional changes and adequacy of nutritional intake; changes in body composition by weight and other anthropometric measures and bioelectrical impedance analysis (BIA); biochemical parameters associated with nutritional status (cholesterol, triglycerides, vitamin B12, and folate); and (2) Explore the extent to which nutritional status serves as a cofactor to impaired immune function during HIV infection and its treatment. The study employs an initial cross-sectional design, comparing different HIV disease severity groups determined by CD4 count and HIV treatment protocols, combined with a longitudinal design, involving follow-up of subjects at monthly intervals for the first eight months and then at decreasing intervals. Recruitment was completed in May 1992, including 120 subjects of whom 13 were females. Data collection was completed in April 1994. Data analysis is in progress. Several substudies have been completed, including: a) Validation of the absence of plasma TNF-alpha in this cohort. b) Consequences of fasting versus not fasting on the accuracy of body composition estimate by BIA. c) Comparison of calculated energy consumption to that measured by indirect calorimetry. d) The effect of timing and pattern of collecting dietary information.